Private Configure message should be more explicit

[victorhurdugaci]

Change the Configure method to private and run:

private void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)

• Expected: an error message saying that Configure should be public
• Actual error message: "A method named 'ConfigureDevelopment' or 'Configure' in the type 'WebApplication1.Startup' could not be found."

[JunTaoLuo]

merged to dev